A circuit board includes an electric insulation board and a circuit pattern formed on the electric insulation board. Such a circuit board is used for mounting components such as electronic components thereon.
Such electronic components may include a heat-generating device such as a light emitting diode (LED) that generates a large amount of heat. Heat generated from such as a heat-generating device increases the temperature of a circuit board and causes malfunction and reliability problems of the heat-generating device.
Accordingly, a radiant heat structure is important for dissipating heat from an electronic component to the outside of a circuit board, and the thermal conductivity of an insulating layer formed on the circuit board has a large influence on heat dissipation. The thermal conductivity of an insulating layer can be increased by filling an inorganic filler in the insulating layer at a high density, and an epoxy resin having a low viscosity is proposed as an inorganic filler.
Resins such as Bisphenol A type epoxy resin and bisphenol F type epoxy resin are generally used as low viscosity epoxy resins. Since such epoxy resins are difficult to handle because such epoxy resins are liquid at room temperature and are disadvantageous in terms of heat resistance, mechanical strength, and toughness.